1. Field of the Invention
The present invention relates to a trouble diagnosing device that diagnoses a trouble of a vehicle such as a track or a bus, as the device is coupled with an ECU (electronic control unit) mounted on the vehicle.
2. Description of the Related Art
As shown in FIG. 7, a trouble diagnosing device for an electronic control system of a vehicle is conventionally known. (See, for example, Jpn. Pat. Appln. KOKAI Publication No. 2002-91545.) As shown in FIG. 7, a trouble diagnosing device 1 is connected via a communication line 2 to a vehicle-installed ECU 3 (electronic control unit). Various commands are transmitted and received between the trouble diagnosing device 1 and the ECU 3 via the communication line 2. The ECU 3 has a diagnosis function. The diagnosis function means a self-diagnostic function. More specifically, the ECU 3 monitors input signals from various sensors, actuator and switch, and when some abnormality occurs in an input signal, the ECU 3 makes a memory 4 store the contents of the abnormality (diagnosis code). When a starter switch (not shown) is turned on to start the engine, thus generated diagnosis code is stored in a current trouble information region of the memory 4 as a current diagnosis code in real time. When the starter switch (not shown) is turned off, the diagnosis code stored in the current trouble information region of the memory 4 is transferred to a past trouble information region of the memory 4, where the transferred code is set as a past diagnosis code, and the current trouble information region is cleared to zero.
The trouble diagnosis device 1 includes a display unit 5, an “S” key 6a, a “C” key 6b, a cursor key 7, an “YES” key 8a, a “NO” key 8b and function keys 9.
The trouble diagnosing device 1 can display a diagnosis code generated while the vehicle is running, on a display unit 5.
For example, when a self-diagnostic mode is set by manipulating a particular key, the trouble diagnosing device 1 transmits to the ECU 3 a command instructing to read the current diagnosis codes stored in the current trouble information region of the memory 4. Consequently, the current diagnosis codes are displayed on the display unit 5 as shown in FIG. 8A. The display unit 5 displays a total of 5 diagnosis codes including “11. common rail pressure sensor”. In the case where more than 5 diagnosis codes are actually stored in the current trouble information region of the memory 4, these codes must be scrolled on the screen by manipulating the cursor key 7. It should be noted that numeral “11” indicates a diagnosis code.
For maintenance, it is necessary to know the past diagnosis codes. To display the past codes, for example, the “S” key 6a was assigned for this operation. As the “S” key 6a is operated, the trouble diagnosing device 1 transmits to the ECU 3 a command of reading out the past diagnosis codes stored in the past trouble information region of the memory 4 of the ECU 3. Consequently, the past diagnosis codes are displayed on the display unit 5.
As described above, in order to display past diagnosis codes on the display unit 5, the key operation described above must be performed, but this operation is laborious and therefore it makes the maintenance work more complicated.
Further, for the repair of a broken-down vehicle, not only current diagnosis codes but also past diagnosis codes are important data. Nevertheless, if one mechanic takes a memo of the information of the diagnosis codes displayed on the display unit 5, and passes it to another mechanic, there results in some cases such confusion that it is not clear as to whether a diagnosis code on the memo indicates a current diagnosis code or a past diagnosis code. When such confusion occurs, it is very difficult to investigate the cause for the trouble.